1. Field of the Invention
The present invention relates to a machining device utilizing a parallel mechanism for supporting a tool using a plurality of link mechanisms.
2. Description of the Related Art
Machine tools to which a parallel mechanism is applied have been developed. Most of the machining devices adopt a structure referred to as "Stewart platform" structure.
The outside view of a parallel mechanism machining device of ordinary Stewart platform structure is shown in FIG. 7 and the typical view thereof is shown in FIG. 8. In FIG. 8, each of adjustable joints 41 (41a to 41f) supporting six links 40 (40a to 40f) at a movable body 20 side has a constitution shown in, for example, FIG. 9 that the rotary shaft thereof is supported by an anti-friction bearing.
In addition, each of adjustable joints 42 (42a to 42f) supporting six links at a fixed platform 34 side has a constitution shown in, for example, FIG. 10 that the rotary shaft thereof is supported by an anti-friction bearing. The links, which are, for example, ball springs, are extensible by rotating nuts by a servo motor. In FIG. 8, reference symbol 19 denotes a table and 21 denotes a tool.
The above-stated Stewart platform structure is characterized in that the structure is simple and has high rigidity of the structure in Z-axis direction (tool rotation axis direction in FIG. 8). Since the movable body 20 serving as a platform is protruded from the fixed base 34, its rigidity in X and Y axis directions is low. Since the table 19 is fixed to the lower surface, the structure has disadvantageously bad chip removal property.